10.1-inch form factor has been adopted by Android tablets, but not Apple’s iPad. A major ramp up in 10.1-inch cover glass manufacturing could indicate high demand for Android tablets.

Touch panel makers TPK Holding, G-Tech and Wintek – all major Apple suppliers – are reportedly ramping up 10.1-inch cover glass manufacturing to ten million units per month, reportsDigiTimes, a trade publication specialized in Asian supply chain. Such a substantial increase is eyebrow raising knowing that the market-leading iPad sports a 9.7-inch display while the 10.1-inch form factor is mostly an Android play.

9to5Google learned that Samsung’s Tabs are selling very well, measured in millions. We also know Amazon is close to launching its tablet and if market sources are correct, the online retailer is eager to ship millions of units in the run-up to Christmas. However, Amazon’s inaugural tablet PC will be a seven-incher, with both TechCrunch and DigiTimes reporting that a 10.1-inch Amazon tablet won’t be out until early 2012.

In any case, that’s a lot of cover glass units for non-iPad devices. Market watchers say Fuji Crystal and Lens Technology supply Apple with an estimated 70 percent of the cover glass, mainly for iPhones. G-Tech and Wintek supply to iPads and TPK Holding is said to provide cover glass to both iPhone and iPad.

Either touch panel makers have overestimated demand (which we doubt), or Apple is switching to 10.1-inch form factor for iPad 3 (highly unlikely, but possible given the hints of four-inch iPhone) or Android makers have decided to blanket the market this holiday season with millions of 10.1-inch tablets, which is the most reasonable assumption.